The Virology Core (Core C) will provide routine laboratory support for Projects 1-4 and the Animal Core (Core A). The Virology Core will work closely with the Nonhuman Primate Core (Core A) and the Molecular Biology Core (Core B) to determine the macaque infectious dose (MID) of several challenge SHIV stocks. Once characterized these stocks will be used to fulfill the specific aims of Projects 1-4. Core C has budgeted for supplies to support Projects 1-4 and Core A. In addition to time lines, individual Project Leaders have provided the Virology Core with detailed lists of routine assays to support their proposed macaque projects. By centralizing laboratory activities in a service core we will minimize supply and reagnt waste as well as duplication of efforts and provide a continuity between projects. The Virology Core is also responsible for the safe operation and maintenance of the biosafety level-3 laboratories, ensuring the most efficient use of this limited laboratory resource.